Diagnosis and management of perineurial (Tarlov) cysts in two dogs

Case 1. A 10-year-old female intact German shepherd dog, presented with a six-month history of progressive neck pain and ataxia of all four limbs. Neurological examination was consistent with a C1-C5 myelopathy. Atlanto-occipital cisternal cerebrospinal fluid (CSF) analysis was unremarkable.

MRI of the neck using a 1.5 T magnet (Echospeed; GE Medical Systems) revealed degeneration of the C5-C6 intervertebral disc with mild dorsal protrusion causing mild right-sided ventro-lateral spinal cord compression; additionally, a 5 mm×6 mm×7 mm oval cystic structure dorsolateral to the spinal cord was noted, causing moderate right-sided dorso-lateral spinal compression at the same level. This lesion was T2 hyperintense, T1 hypointense, T2 FLAIR hypointense (all when compared with the spinal cord) and non-contrast enhancing.

A right-sided dorsal laminectomy was performed at C5-C6. The cystic lesion, originating from the dorsal nerve root lateral to the dorsal root ganglion, was fenestrated and a biopsy was obtained, taking care to avoid dorsal nerve root damage. Recovery was uneventful and the dog was neurologically improved at the time of discharge, but was lost to follow-up thereafter.

The biopsy consisted of a folded cystic structure consisting of a wall of moderately cellular fibrous tissue showing an orderly arrangement of parallel bundles of fibroblasts. There was no distinct epithelial lining. There was some pale amorphous basophilic material within some parts of the cystic cavities. In places, there were very small numbers of lymphocytes in the cyst wall and little hemosiderin deposition. No nerve fibres or ganglion cells were present. Localisation of the lesion and histopathology were consistent with a perineurial cyst.

Case 2. A 10-year-old female intact Labrador retriever, presented with a two-month history of intermittent but progressive non-weight-bearing lameness of the right pelvic limb and pronounced radicular pain. Orthopaedic examination was considered normal. Neurological examination was unremarkable except for marked discomfort on palpation of the lumbo-sacral …